Orthopedic fixation devices such as plates are frequently coupled to bone with fasteners inserted through plate holes. It is known that securing such fasteners to the bone plate, for example through the use of expansion-head screws, can decrease the incidence of loosening of the fixation assembly post-operatively. It is also known that a bushing may be disposed in each plate hole to receive the fastener to permit polyaxial movement so that the fastener may be angulated at a surgeon-selected angle. However, typically as the fastener is inserted into bone through the bushing and plate hole, a threaded head of the fastener engages a threaded internal surface of the bushing to expand the bushing against the wall of the plate hole, thereby locking the screw at a given angular orientation with respect to the plate.
Despite these fixation systems, there exists a need for bone plates that allow post-operative angulation and/or movement. In particular, with respect to fixation of the spine, there exists a need for anterior cervical compression plates and associated fasteners that allow the vertebral bodies to compress over grafts post-operatively. In order for compression to occur, there exists a need for a plate/fastener construct that allows for translational and/or rotational settling that both occur post-operatively between the plate and fasteners that have been rigidly placed into vertebral bodies. More particularly, there exists a need for a fixation system that facilitates translational settling by permitting a fastener to slide within a plate hole. There further exists a need for a fixation system that facilitates rotational settling by permitting a fastener head to toggle or pivot within the plate hole. In addition, there exists a need for a fixation system that permits fastener motion associated with translational and/or rotational settling while also resisting back-out of the fastener from the plate.